bearings work against the journal which has a fixed size in relation to the load rating of the particular axle
design. In table I, the AAR axle designations are given along with the axle sizes and the corresponding load
ratings for new passenger car axles when trains run at speeds up to 85 mph and above 85 mph. For example,
AMR axle D has a journal 5 1/2 inches in diameter and 10 inches long. This axle's load capacity is rated at
34,000 pounds at speeds up to and including 85 mph; however, from 86 to 100 mph its capacity is rated at only
32,000 pounds. Besides the AAR axle designations A through F, there are three basic types of axles. Each type
has prescribed markings, dimensions when new, wear limits, and possible defects that can cause the axle to be
withdrawn from service. These are explained in this section in the order mentioned.
Table I. Axle Designations and Load Ratings.